1. Field of the Invention
The present invention relates to the field of cargo handling, and in particular, to the rapid transportation and loading of cartons of frozen animal products onto a refrigerated vessel.
2. Background of the Invention
While there have been significant advances in the methods employed for the loading and unloading of vessels, the loading of refrigerated, cartonized cargo, and in particular, frozen animal products has proved particularly difficult due to several intractable problems. As a result, the transfer of the products from the packers to their loading aboard a vessel is presently carried out by processes that involve high costs and significant expenditure of manual labor, and which include bottlenecks that slow the process, that may result in product degradation or spoilage, and that result in long loading times for the product onto the vessel. It is presently common for the handling of cartons of frozen animal products to proceed as follows.
A large volume of animal products such as frozen chicken, turkey, beef, pork and seafood products (including livers, hearts, parts, deboned meat and the like) are frozen and shipped in and from the U.S. in relatively flat boxes. For example, chicken thighs, legs or quarters may be shipped in cartons of about 23.5 inches in length by 16.5 inches in width by 4 to 6.25 inches in height (59.7 cm by 41.9 cm by 10.2 to 15.9 cm). A preferred standardized box size for use with this invention, however, would be 24 inches by 16 inches (61.0 cm by 40.6 cm) with the height of the box varied to hold the particular products to be shipped. A box of such chicken parts may weigh on the order of 35 to 45 pounds (16 to 20 kg).
For simplicity, reference will hereafter be made to cartons of chicken parts, as other animal products may be handled in a similar manner.
Owing to the size restrictions imposed by standard trucks and trailers, the cartons are normally stacked on 40xc3x9748 inch (102xc3x97122 cm) pallets in layers of five cartons arranged with two cartons placed on the pallet in an end-to-end relationship beside three cartons placed side to side with their long axes perpendicular to those of the first two cartons. A palletload of cartons generally contains between about 10 to 12 such layers of cartons.
The packer sends the fresh chicken parts in such palletloads to a blast freezer/cold storage warehouse. At the warehouse, the cartons are restacked with spacers between the layers thereof. The spacers allow the circulation of air between the layers of cartons. Once the cartons are so stacked, the palletload of cartons are transferred to a blast freezer, which forces air chilled to about xe2x88x9240xc2x0 F. (xe2x88x9240xc2x0 C.) between and around the cartons. When the freezing process is completed, the cartons are removed from the blast freezer and placed in a rotator. The load of cartons is then rotated 90 degrees onto its side, the spacers are removed, and the load of cartons is then rotated back to an upright position in which it rests once more on the pallet. In order to facilitate transportation and storage of the stacks of cartons, the stack may be wrapped with a stretchable plastic film to help prevent excessive sliding of the layers of cartons relative to one another. Lift trucks are then used to move the cartons of frozen chicken products and transport them into the cold storage warehouse.
When the time comes to load a ship, lift trucks are used to remove the palletloads of cartons of chicken parts from the warehouse, and tie cartons are placed inside dry van trucks or truck trailers for transportation to the dock. These are typically uninsulated and unrefrigerated, and thus can be deleterious to the frozen product contained therein. At the dock, the cartons are removed from the truck trailer and placed on the dock, where they are subsequently lifted into the hold using the ship""s gear, such as by using slings, lifting platforms or flying forks to lift the cartons and pallets.
In the hold, lift trucks engage the pallets and transport the pallets with their stacks of cartons to locations near where the cartons will be stowed. Stevedores then manually remove the cartons from the pallets and stack them without pallets for shipping. The pallets are then returned to the square of the hatch and are stacked to be hoisted out of the hold and back onto the dock by the ship""s gear. The square of the hatch is the volume of space extending vertically downward from the open hatch to the floor of the cargo hold.
This process is quite inefficient. Delays in bringing a sufficient quantity of product to the dock and in unloading the cartons from the truck can increase the time needed to load the vessel. The space constrictions in the vessel limit the number of workers who can be engaged in stowing of the cartons, and thus may create a backup for product arriving at the dock. Excessive delays in loading which result in the cartons being left on the dock or in the truck can allow the product to begin to thaw, which can result in spoilage or otherwise render the product unmarketable. Delay in loading may also result in increased condensation of moisture on the cartons which can complicate the handling process. As the industry is seeking to use less wax on the cartons and to utilize paper-coated boxes, the damaging effect of condensation and internal thawing on the boxes is increased.
The breakage rate for pallets during this process is fairly high. As many as half of the pallets may suffer some breakage, and this can result in splintered wood, which may contain protruding nails, being left at the warehouse, on the dock or in the cargo hold of the vessel. Additional work is thus required to collect the pallets and pallet debris, to extract it from the hold of the ship or remove it from the dock, and to repair or discard the broken pallets. Further, the existence of pallet debris at the warehouse, on the dock, and in particular in the hold of the vessel, presents a risk of injury to workers.
Inefficient as this method of handling may be, there are a number of constraints that have made it difficult to improve. The main problems encountered is that the holds of the ship are irregular both in the overhead clearance and in the shape of the floor space. Not only does the overhead clearance of the cargo holds vary from ship to ship, and perhaps within a ship from hold to hold, the internal structure of the vessel and of the cooling system within it can result in overhead clearances that vary depending on the location within the hold.
Another difficulty in loading such cargoes is that the cartons are typically stacked to a uniform height after freezing. This is necessary for efficient use of the cold storage warehouse. This uniform height is generally ten or twelve layers of boxes arranged on a lift truck pallet, but it may vary somewhat from this number depending on the size of the cartons. The cartons are unitized by wrapping them with a stretchable plastic film that aids in transportation of the palletloads by fork lift, etc. However, space on refrigerated vessels is at such a premium that the wasted space of such pallets is considered undesirable. Thus, it has been considered necessary to avoid stowing the cartons on the pallets, and thus it has been the practice to stow the cartons in the ship by restacking them without the pallets within the ship. Moreover, since the ceiling height of holds on ships varies, and is seldom equal to the height of the cartons when stacked for warehousing purposes, it has heretofore been considered essential to manually stack the cartons in order to obtain as complete a filling of the vessel as possible.
The present invention provides a method for transportation of cartons of frozen products from the blast freezer/cold storage warehouse into a refrigerated vessel. The method may be practiced as follows.
As mentioned above, in preparing cartons of animal products and the like for freezing, the cartons are restacked on a pallet with spacers between the layers of cartons. The spacers permit the flow of cold air between the layers of the pallets and thus facilitate the rapid freezing of the product. At this stage, as the cartons require restacking with the spacers, a sling pallet may be used under the stack to be frozen.
A sling pallet, namely, a pallet with two or more channels in its upper surface, each of which extends from a first side of the pallet to the opposite side may be used in the present method. Preferably, the channels are parallel to one another and are symmetrically disposed with respect to the upper surface of the pallet. Changing to sling pallets at this stage permits the ordinary pallets to be stacked and returned to the producer.
Although it is the general practice to use pallets having dimensions of 40xc3x9748 inches (102xc3x97122 cm) in the frozen chicken parts industry to allow loading thereof into enclosed vans or trailers, the method of the present invention permits the use of 48xc3x9748 inch pallets (122xc3x97122 cm), which hold six rather than five cartons per layer. If such a layout is to be used, of course, and if restacking of the cartons is performed to accomplish this transformation, the cartons could be restacked on a sling pallet at that time. On the smaller pallet, the first layer of boxes is arranged with two cartons adjacent one side of the pallet in end to end alignment. Three cartons in a side-by-side arrangement are placed adjacent the other edge of the pallet (the two by three stacking pattern). The cartons should be stacked on the pallet such that the channels in the pallet extend longitudinally under the two end-to-end cartons and transversely under the three side-by-side cartons. For the larger pallets, where the cartons are arranged in two rows of three side-by-side cartons, one channel should run under each such row transversely to the long axes of the cartons. The next higher layer would have the same pattern, but would be rotated ninety degrees, and the layer on top of that would be identical in layout and orientation to the first layer (the three by three stacking pattern). This is the preferred configuration.
After the cartons are stacked with spacers between layers, the contents of the cartons are frozen in the blast freezer. The pallet and stacks of cartons are then placed in a rotator to facilitate removal of the spacers. It is also possible to replace a standard pallet with a sling pallet at this stage, rather than stacking the cartons with the spacers on the sling pallet as discussed above, although the configuration of the boxes cannot be changed from five boxes per layer to six boxes per layer at this stage without restacking.
After removal of the spacers and re-rotation of the palletload of cartons, the cartons may be wrapped with stretchable plastic film and slings may be inserted about the stack of cartons. The cartons may then be transported for storage in the refrigerated warehouse by means of lift trucks or other transportation means.
When the time for loading of a vessel comes, the palletloads of cartons are removed from the cold storage warehouse and loaded onto a truck for transportation to the dock. Preferably, the slings are placed on the stacks of cartons before they are loaded onto the truck, although the slings could be installed at the dock. Rather than loading them into uninsulated, enclosed trucks or trailers for transportation to the docks, as in the prior art method, the palletloads of cartons are loaded onto flatbed trucks or the flatbed trailer of a tractor-trailer truck and an insulating blanket of any known type which is adequate to protect the cartons against excessive warming is placed over them to reduce warming and possible melting that could occur in the uninsulated trucks. Hold-down straps may then be fastened over the stacks of cartons and blanket and tightened using the known belt and winch systems. Alternatively, if the blanket is of a sufficiently strong material or construction, the blanket itself could be used as a hold-down for the stacks of cartons and the blanket could be fastened down tightly atop the cartons. This might be accomplished, for example, by affixing straps of webbing in positions corresponding to winches on the trailers which extend beyond the edge of the blanket and pulling these tight with winches.
The trucks are then driven to the dock and positioned alongside the ship, where the ship""s gear is used to lift the preslung stacks of cartons by their slings off of the truck and load them directly into the cargo hold. Since the cartons are lifted by the slings, the pallets remain on the truck and can then be transported directly back to the blast freezer/cold storage warehouse for further use. This direct loading of the ship from the flatbed truck eliminates the need for loading the cartons off the truck and onto the dock. This is important, as it reduces the amount of time the cartons are exposed directly to the ambient air and humidity, reducing the likelihood of thawing and of accumulation of condensation. Furthermore, the elimination of the need to unload trucks out onto a dock and thereafter load them into the ship eliminates delays in feeding the cargo into the ship. This is also important to the practice of the present invention since the improved efficiency in stowage provided by the present invention can only be fully utilized if the cargo can be loaded on board with sufficient speed to keep pace with the increased speed of the stowing operation.
The ship""s gear deposits the cartons in the hold onto a special landing pad. This is a sling/lift truck pallet that can receive the cartons but which has channels to receive the slings so that the slings may be removed from the stacks of cartons. The landing pad also permits the stacks of cartons to be picked up directly by a load push lift truck owing to the existence of open-top channels into which the blades (or platens) of the lift truck may be inserted.
A load push lift truck, has at least two and preferably three blades extending from its lift mechanism. Preferably, the three blades are relatively broad, and have smooth, polished upper surfaces to facilitate the sliding of the cartons thereon. A push plate associated with the lift mechanism which can be extended by means of hydraulic cylinders from a retracted position adjacent the lift mechanism to a position adjacent the ends of the blades is used to extract the blades from under the cargo. Preferably, such a lift truck includes a side-shift mechanism which permits small lateral adjustments in the position of the cargo to facilitate its precise placement. Such load-push lift trucks are known in the art of specialized lift trucks.
When a cargo is landed on the landing pad, the slings may be removed from the stack of cartons. The load push lift truck positions the push mechanism in its fully retracted position and slides its blades between the blocks of the landing pad. Thereafter, the entire stack of cartons is transported to its stowage location. If the stack is to be positioned on the floor of the cargo hold, the operator maneuvers the load into position, possibly using the side shift mechanism to position it against an adjacent stack or wall, and activates the load push mechanism while backing the lift truck away from the location or allowing the load push mechanism to push it away from the stack of cartons. Additional layers of cartons can then be manually stacked on top of the cartons to fill the hold from floor to ceiling from stacks of cartons transported to a nearby location by the load push lift truck.
Attentively, in order to reduce the amount of lifting required by the stevedores, the lift truck may first position stacks of cartons in areas to be filled. The stevedores then commence manual stacking of layers of cartons on the floor of the vessel by removing some of the layers of cartons from the stacks deposited by the load push lift truck. Once the desired number of layers have been laid down such that a full stack of cartons will fill the remainder of available space to the ceiling, the load push lift truck can then deposit full height stacks of cartons on top of such partial stacks to complete the stowing process at that location.
When the loading of the hold is completed except for the area under the square of the hatch, the load push lift truck, removed slings, if any, and landing pad may be removed from the hold. Thereafter, the square of the hatch may be filled by landing stacks of cartons therein using the ship""s gear. In the absence of a landing pad, the slings may not be easily removable from the stacks of cartons so landed. As such, in order to speed the loading of the square of the hatch, the slings may be left in place. Some manual restacking of cartons to fill the square of the hatch may of course be necessary in order to avoid the wasting of space in the cargo hold.
A number of operators of cold storage facilities have the practice of moving all of their frozen chicken to the dock in refrigerated trucks. As most of such trucks will not accept a 48xc3x9748 inch (122xc3x97122 cm) pallet, 40xc3x9748 inch (102xc3x97122 cm) pallets are commonly used. The use of such refrigerated trucks for transporting the frozen chicken may be used for a variety of reasons. For example, the cold storage warehouse may be located too far from the dock to allow for unrefrigerated transportation.
Regardless of the reason, however, the result is that a large amount of the frozen chicken produced is shipped on 40xc3x9748 inch (102xc3x97122 cm) pallets. As a result, the two by three stacking method is used. These pallets are typically loaded such that the long axis thereof is parallel to the long axis of the truck. The top and bottom boards that make up the upper and lower surfaces of the traditional pallet generally are of 40xe2x80x3 length and run transversely to the long axis of the pallet. It is not possible to convert such a pallet to a sling pallet by removal or repositioning of the top boards. As the channels for a sling pallet must run parallel to the long axis of the 40xc3x9748 inch (102xc3x97122 cm) pallet in order to be positioned parallel to the long axis of the two end-to-end boxes in the two by three pattern, and as the boards of the more typical 40xc3x9748 inch (102xc3x97122 cm) pallet run transverse to the long axis, removal of planks would not result in channels through which slings could be extended. Planks could be removed from the bottom of the pallet and, with some clearancing, channels could be made to allow insertion of the forks of a lift truck to permit the pallet to be picked up by a lift truck from any side.
This problem may be overcome in the present invention by the use of one or more dockside rotators that are capable of rotating, or tipping, one or more palletloads of frozen chicken onto its side. Preferably the palletload(s) of frozen chicken are rotated by 90xc2x0 or more, and preferably by about 100xc2x0. This permits the pallet to be removed easily. The rotator may have channels in appropriate locations to permit slings to be positioned such that, when the stack of cartons of frozen chicken is rotated back to an upright position, the slings may be connected to a hook or spreader bar lowered by the ship""s gear and the stack of frozen chicken may be lifted, without a pallet, into the hold of the ship.
Of course, where the stacks of frozen chicken will be rotated through more than 90xc2x0, and even if the stacks of frozen chicken are only rotated 90xc2x0, it is preferred to provide means for preventing the stack from sliding too far away from the pallet upon rotation, and to prevent cartons of frozen chicken from falling from the top of the stack. This can be accomplished by providing the rotator with adjustable retaining bars that can be opened and closed, as desired.
The rotator mentioned above may be configured to rotate one, two or more stacks of frozen chicken at a time. Preferably, the rotator is operated hydraulically, in which case electric or diesel-powered hydraulic pumps may be used to provide the pressurized hydraulic fluid. The retaining bars may also be opened and closed hydraulically.
Calculations based on the speed with which a truck can be unloaded using fork lifts and the cycle time typical of ships"" gear, there is adequate time to perform the rotating of the palletloads of frozen chicken, the removal of the pallets, the placement of the slings and the re-rotation of the stack of cartons of frozen chicken to an upright position.